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[ratio.ratio] What is sign? #5879

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JohelEGP opened this issue Oct 2, 2022 · 5 comments · Fixed by #5925
Closed

[ratio.ratio] What is sign? #5879

JohelEGP opened this issue Oct 2, 2022 · 5 comments · Fixed by #5925

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@JohelEGP
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JohelEGP commented Oct 2, 2022

(2.1)
num shall have the value sign(N) * sign(D) * abs(N) / gcd.
@jwakely
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jwakely commented Oct 2, 2022

Signum: https://en.m.wikipedia.org/wiki/Sign_function

@JohelEGP
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JohelEGP commented Oct 2, 2022

Is it supposed to be defined by a normative reference? It's not defined by the WD.

@JohelEGP
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JohelEGP commented Oct 2, 2022

Based on https://eel.is/c++draft/intro.defs p1-p2, searching the databases does not show sign being defined by ISO/IEC 2382 nor ISO 80000-2:2009.

@jwakely
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jwakely commented Oct 2, 2022

It might be in ISO/IEC 10967, Language independent arithmetic (LIA) but I think we only refer to that in footnotes.

@JohelEGP
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I see that ISO 80000-2:2019 does define sgn (with verbal equivalent signum, Table 6, item no. 2-10.13).

@JohelEGP JohelEGP mentioned this issue Oct 30, 2022
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[ratio.ratio] Use defined function for sign JohelEGP/draft
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@jwakely @JohelEGP